Miosis Eye: Definition, Causes, and Symptoms

Miosis Eye: Definition, Causes, and Symptoms
Miosis - Photo by Noelle Otto from Pexels

Tripboba.com - A pair of eyes is like the most important part of the human body. As an organ of the visual system, eyes direct us to our daily activities through its capability to receive and process visual detail to our brain.

Because it's very essential, we need to keep our eyes healthy as much as we can. This way, we will have good eyesight for a long time.

To help maintain eye health as you age, you need to follow every advice, such as doing good habits and consuming nutritious foods.

If you don't take good care of your eyes, you will be likely experiencing eye problems. Several kinds of eye problems occur because of bad habits. But, there is also a possibility it happens because of genetic factors.

Miosis is one of the most common eye problems. You might have heard this term so often. So, what is it actually? What causes miosis and what are the symptoms that happen? To answer your curiosity, let's read down this page thoroughly to find out about miosis.

1. Miosis definition

Miosis is an eye problem that is characterized by excessive constriction of the pupil. Miosis is also known as myosis. The diameter of the pupil will be less than 2 millimeters (mm), or more than 1/16 inch.

If you don't know which part a pupil is, it is a circular black dot in the middle of the eye that allows light to enter. Besides, the one that is responsible for controlling the diameter and size of the pupil is called iris.

Miosis can occur in one or both eyes. It's also called anisocoria when miosis affects one of your eyes. The pinpoint pupil is another name for miosis. Meanwhile, it is called mydriasis when your pupils are too broad.

Several things trigger miosis. Miosis can occur as a result of consuming different kinds of drugs and chemical materials. Chemicals that can trigger miosis are including fentanyl, morphine, heroin, and methadone.

2. Miosis causes

As we mentioned before, people who suffer from miosis have different causes. It can be a genetic factor, bad habits, or any other causes. Below is a complete explanation of miosis causes.

a. Age

The eyes of newborn babies have extra protection from bright light, normal for young children to remain small for around two weeks. But, as they age, the baby's pupils develop premature miosis. The muscles that train these pupils cannot help much. It will make it difficult for the baby to see it at night.

b. Inflammation

Swelling in the eye is another factor that causes miosis. This inflammation can also occur because your eyes hurt. Uveitis is also a cause of miosis in humans. Uveitis is swelling in your iris, the part that is responsible for controlling the diameter and size of the pupil.

c. Side effects of the medicine

There are several drugs and chemicals that are prone to cause miosis, including:

  • Fentanyl
  • Oxycodone (Oxycontin)
  • Codeine
  • Heroin
  • Morphine
  • Methadone

d. Genes

Congenital miosis or microcoria is an event where you are born without muscles that control your pupils or with pupils that are not correctly formed. This will occur if one or both of your parents pass down the problem gene to you. Miosis can occur in one eye or both. Having trouble seeing things far away, and you might also be shortsighted. 

e. Horner's syndrome

If you have miosis and the cause is Horner's syndrome, this is a rare occurrence. This Horner's syndrome affects how your brain "talks" to one side of your face, including one of your eyes.

It will make one of your pupils looks small. That can happen after a neck injury or neck surgery that someone inherits from their parents.

3. Miosis Symptoms

Symptoms that accompany miosis are as follows:

a. Cluster headaches

This headache can be very severe around or over the eyes, or forehead. Depending on the type of cluster headache you have (chronic or episodic), this occurs only on one side of your head and recurs at different intervals.

b. Intracranial hemorrhage and brain stem stroke

Common symptoms of intracranial hemorrhage or brain stem stroke (Pontine) are a symptom of myosis in both pupils. These accompanying symptoms occur when the blood supply to your upper brain stem (Pons) is interrupted by a ruptured or blocked artery.

c. Horner's syndrome

It is a symptom that occurs that results from damage to the nerves that connect the brain to the face or eyes. Eyelid drooping on one side of the face and decreased pupil size are typical symptoms.

d. Iris inflammation (iridocyclitis)

This inflammation has many causes. It includes:

  • HIV
  • rheumatoid arthritis
  • psoriasis
  • Tuberculosis
  • shingles (shingles)

e. Neurosyphilis

Neurosyphilis is when untreated syphilis infection continues into the brain. These symptoms also attack the nervous system at any stage of the disease.

f. Lyme disease

It shapes a bottle opener similar to syphilis spirochete, Lyme disease is caused by infection with bacteria. 


  1. 36 Questions That Lead to Love: With Tips How to Do It Properly!
  2. Best 75+ Who Knows Me Better Questions To Ask To Your Friends And Family!
  3. 110+ Patriotic Independence Day Greetings to Complete Your Independence Day Celebration
  4. 80+ Dad Jokes 2020 and Other Dad Jokes That Will Crack You Up
  5. 150+ Funny Questions to Ask on Instagram Story to Build A Deeper Relationship with Your Followers